Electric machine with stator windings having over-under end loops

ABSTRACT

A multi-phase electric machine having plurality of windings are mounted on the stator core and define a plurality of phases with each phase having at least two parallel windings. A standard pitch is defined between each pole of each phase, the pitch being a common circumferential spacing between corresponding slots of each pole. Each of the windings has a position change end loop at the same location, wherein the position change end loops define a non-standard pitch to thereby change the relative positions of the parallel windings in the slots. At each set of such position change end loops, the windings defining a greater pitch extend over the windings defining a lesser pitch.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims priority under 35 U.S.C. 119(e) of U.S. provisional patent application Ser. No. 62/368,070 filed on Jul. 28, 2016 entitled ELECTRIC MACHINE WITH STATOR HAVING PHASE SHIFT WINDINGS; U.S. provisional patent application Ser. No. 62/368,104 filed on Jul. 28, 2016 entitled ELECTRIC MACHINE WITH STATOR HAVING EVEN SLOT DISTRIBUTION; and U.S. provisional patent application Ser. No. 62/373,223 filed on Aug. 10, 2016 entitled ELECTRIC MACHINE WITH STATOR WINDINGS HAVING OVER-UNDER END LOOPS; the disclosures of each of which are hereby incorporated herein by reference. This application is related to U.S. patent application Ser. No. 15/652,507, filed Jul. 18, 2017 entitled ELECTRIC MACHINE WITH STATOR HAVING PHASE SHIFT WINDINGS and U.S. patent application Ser. No. 15/652,388, filed Jul. 18, 2017 entitled ELECTRIC MACHINE WITH STATOR HAVING EVEN SLOT DISTRIBUTION.

BACKGROUND

The present invention relates to electric machines.

Electric machines are used for several different purposes in modern vehicles. For example, electric machines are commonly employed as starters, alternators, traction motors and for other purposes. In these applications, the electric machine may act as a motor, generator or be selectively operable as either a motor or a generator.

There is an increasing demand for electric machines used in vehicle applications, as well as other non-vehicular applications, for an electric machine with reduced size and increased efficiency.

Improvements in electric machine design which allow for cost efficient manufacture while meeting the increasingly stringent demands of modern vehicular applications are desirable.

SUMMARY

The present invention provides an electric machine having a winding pattern with end loops that alter the relative position of the individual windings of a phase having a plurality of parallel windings and which allows for the cost efficient manufacture of a compact and efficient electric machine.

The invention comprises, in one form thereof, a multi-phase electric machine that includes a stator operably coupled with a rotor wherein the rotor is rotatable relative to the stator. The stator includes a stator core defining a central opening and a plurality of axially extending slots which circumscribe the central opening. A plurality of windings are mounted on the stator core wherein the plurality of windings define a plurality of phases and wherein, for each phase, the plurality of windings include at least two parallel windings. The stator assembly defines a standard pitch between each pole of each phase, the pitch being a common circumferential spacing between corresponding slots of each pole. Each of the parallel windings includes at least one position change end loop, wherein each of the parallel windings has one of the position change end loops at the same location, wherein the position change end loops define a non-standard pitch to thereby change the relative positions of the parallel windings in the slots.

In some embodiments, each phase includes at least three windings connected in parallel. In such an embodiment having at least three windings, the position change end loops may be arranged such that a first set of position change end loops is disposed between a selected pole and an adjacent pole and wherein a first winding of the first set of position change end loops is disposed at one of the clockwise and counterclockwise ends of the pole at the selected pole and is disposed at the other of the clockwise and counterclockwise ends of the pole at the adjacent pole, the remaining windings of the first set of position change end loops each being shifted one by one slot.

In some embodiments the windings may be arranged such that the first winding defines a pitch that is greater than the standard pitch between the first and second poles and the remaining windings each define a pitch that is one less than the standard pitch between the selected and adjacent poles. In such an embodiment, the first winding may extend over the remaining windings between the selected and adjacent poles. When such an embodiment has exactly three windings per phase, the first winding may define a pitch that is two slots greater than the standard pitch between the selected and adjacent poles.

In some embodiments having three windings wherein the first winding moves from one end of the selected pole to the opposite end of the adjacent pole, the first winding defines a pitch that is less than the standard pitch between the selected and adjacent poles and the remaining windings each define a pitch that is one greater than the standard pitch between the selected and adjacent poles. In such an embodiment, the remaining windings may extend over the top of the first winding between the selected and adjacent poles. When such an embodiment includes exactly three windings per phase, the first winding may define a pitch that is two slots less than the standard pitch between the selected and adjacent poles.

In some embodiments of the electric machine, at each set of position change end loops, the windings defining a greater pitch extend over the windings defining a lesser pitch. In such an embodiment, the windings may define a phase shift wherein for each pole, there are a greater number of slots than windings. Such an embodiment may also include windings wherein each winding includes a plurality of position change end loops.

In the various embodiments described above, the electric machine may be a three phase electric machine.

BRIEF DESCRIPTION OF THE DRAWINGS

The above mentioned and other features of this invention, and the manner of attaining them, will become more apparent and the invention itself will be better understood by reference to the following description of an embodiment of the invention taken in conjunction with the accompanying drawings, wherein:

FIG. 1 is a partial winding diagram showing three wires defining a part of an individual phase.

FIG. 2 is a partial winding diagram showing three wires that are connected in series with the wires depicted in FIG. 1 to form an individual phase.

FIG. 3 is a top view of a stator diagram illustrating the arrangement of the wires of FIGS. 1 and 2.

FIG. 4 is a detail view of a portion of the stator diagram of FIG. 3.

FIG. 5 is another detail view of a portion of the stator diagram of FIG. 3.

FIG. 6 is a cross sectional view of an electric machine.

FIG. 7A is a side view showing three standard pitch end loops.

FIG. 7B is a top view showing three standard pitch end loops.

FIG. 7C is a perspective view showing three standard pitch end loops.

FIG. 8A is a side view showing position change end loops with two end loops extending over a third end loop.

FIG. 8B is a top view showing the end loops of FIG. 8A.

FIG. 8C is a perspective view showing the end loops of FIG. 8A.

FIG. 9A is a side view showing position change end loops with one end loop extending over two other end loops.

FIG. 9B is a top view showing the end loops of FIG. 9A.

FIG. 9C is a perspective view showing the end loops of FIG. 9A.

FIG. 10A is a top view showing one end loop extending over two other end loops.

FIG. 10B is a perspective view showing the end loops of FIG. 10A.

Corresponding reference characters indicate corresponding parts throughout the several views. Although the exemplification set out herein illustrates an embodiment of the invention, in one form, the embodiment disclosed below is not intended to be exhaustive or to be construed as limiting the scope of the invention to the precise form disclosed.

DETAILED DESCRIPTION

FIG. 6 illustrates an electric machine 20. In the illustrated embodiment, electric machine 20 is an automotive alternator capable of operating as a motor or as a generator, however, alternative embodiments may take the form of an electric machine that is solely operable as a motor or solely operable as a generator. Electric machine 20 includes a rotor 22 mounted on a shaft 24 which both rotate relative to stator 26. Stator 26 has a stator core 28 and a plurality of windings 30.

Stator core 28 may be formed out of a stack of laminations and defines a plurality of slots 32. Windings 30 include axially extending segments 34 that are disposed within slots 32 and end turns 36 with each end turn 36 connecting a pair of slot segments 34. Axially extending slots 32 circumscribe central opening 38 of stator core 28.

The illustrated embodiment is a three phase electric machine with six turns. Additionally, each phase includes three windings arranged in parallel. In other words, each winding extends about the full circumference of the stator core six times and there are three such windings for each phase. To achieve this arrangement two separate wires or filars are used for each winding whereby a total of six separate wires or filars are used for each phase. Each of the individual wires form three turns about the stator and is connected in series with another one of the wires to thereby form one of the three windings of each phase.

One parameter that may be used to describe a winding arrangement is slots per pole per phase. This is equal to the number of slots per pole in each slot group of the winding if each such slot were filled solely by windings of one phase. For example, in the illustrated embodiment, there are 18 slot segments in each slot group and each slot holds 6 slot segments therefore the illustrated arrangement has 3 slots per pole per phase. The illustrated embodiment, however, has what is known as a phase shift and some slots hold slot segments of two different phases.

The use such phase shifting can reduce what is known as the skin effect. As a general rule, when the conductors in a particular slot carry different phase currents, the skin effect in such conductors will be less than if all of the conductors in the slot carried the same phase current. While such phase shifting reduces the skin effect, the use of such phase shifting can make it more difficult to electrically balance the windings.

To avoid or minimize a re-circulating current in the winding, it is desirable for the winding to be electrically balanced this is particularly true for a winding having a plurality of wires connected in parallel. Providing an electrically balanced stator can be particularly difficult if phase shifting is employed and each phase is formed by an odd number of windings arranged in parallel.

The illustrated embodiment provides a stator winding pattern which provides an electrically balanced stator with phase shifting and an odd number of windings arranged in parallel for each phase. As mentioned above, the illustrated winding pattern includes six turns and three separate windings for each phase. The pattern has three slots per pole per phase but windings occupy four physical slots for each pole or slot group. In each slot group, the two center slots each have six conductors which are all from the same phase. The two outer slots each have three conductors from one phase and three additional conductors from a different phase. To electrically balance the stator, each slot of the slot group needs to have an equal number of conductors from each of the three windings. It is also desirable for each of the different radial layers to have an equal number of conductors from each of the three windings.

This radial balancing, however, is less important than the balancing between slots. The exemplary winding pattern can be used to provide an electrically balanced stator and is further described below with the aid of FIGS. 1-5.

FIG. 1 illustrates three separate wires X, Y, Z that are connected in series with the three separate wires A, B, C illustrated in FIG. 2. More specifically, wire A is connected in series with wire Z to form a first winding, wire B is connected in series with wire X to form a second winding and wire C is connected in series with wire Y to form a third winding. The first, second and third windings are then connected in parallel to form one phase of electric machine 20. Electric machine 20 is a three phase electric machine and two additional phases having the same winding arrangement are also employed with electric machine 20.

As can be seen in FIG. 3, each phase of the stator assembly defines 16 poles with each pole being formed by four physical slots. Six wires fit within each axially extending stator slot 32. As used herein, the radially outermost wire is in layer 1, layer 2 being the next radially inward wire position and so on with the radially innermost wire position being layer 6.

As can also be seen in FIG. 3, as well as FIGS. 4 and 5, each of the poles is formed by a group of four slots wherein the two central slots are each completely filled with windings (six windings in the illustrated embodiment) and two outer slots that are only half filled with windings from a particular phase (three windings in the illustrated embodiment) to thereby form a 3-6-6-3 winding pattern. As used herein, and as labelled in FIG. 4 for slot 15 and slot 3, starting at the outer slot on the counterclockwise side of each slot group forming a pole and moving clockwise, the slots are referred to as slot AA, slot BB, slot CC and slot DD. In other words, slots BB and CC form the central slots and slots AA and DD form the outer slots.

The distance between slot AA of one pole and slot AA of the adjacent poles is 9 slots. Similarly, the distance between slot BB of one pole and slot BB of the adjacent poles is 9 slots and so on, this distance between corresponding slots of the slot groups forming adjacent poles defines the standard pitch of the electric machine. In the illustrated embodiment, the standard pitch is 9 slots.

Returning to FIGS. 1 and 2, the wiring diagrams label any pitch between slot segments that is non-standard. The location of the number indicating the non-standard pitch also indicates at which axial end of the stator the end loop forming the non-standard pitch is located. It is also noted that the wiring diagrams of FIGS. 1 and 2 also indicate in which layer position the wires are located.

As most easily seen in FIGS. 3-5, the windings in slot AA are positioned in the radial outermost layers, i.e., layers 1, 2 and 3 while the windings in slot DD are positioned in the radial innermost layers, i.e., layers 4, 5 and 6. When all of the phases have this same pattern, slot AA of one phase will correspond and overlap with slot DD of an adjacent phase allowing the outer slots to be completely filled with windings. FIGS. 3-5 illustrate the windings of only one phase except for the space between poles 2 and 3 of FIG. 4. This portion of FIG. 4 illustrates the location of the windings from a second phase (indicated by filled-in wire outlines) and the location of the windings from a third phase (indicated by the hollow wire outlines). This clearly shows how the outer slots of each phase overlap such that each outer slot includes windings from two different phases.

It is further noted that while the outer slots of the illustrated embodiment have windings wherein the windings from one phase are all positioned in the radially outer most layers and the windings from the other phase are all positioned in the radially innermost layers, other configurations are also possible. For example, the windings from the different phases could alternate. In the illustrated embodiment this could be achieved by having windings in layers 1, 3 and 5 in slot AA and in layers 2, 4 and 6 in slot DD. Such an arrangement, however, would be more difficult to manufacture than the illustrated embodiment and would require a more complex winding pattern.

To control the position of the windings in the outer slots, special end loops referred to herein as phase shift end loops are used. In the illustrated embodiment, each phase includes three windings that are connected in parallel. With each winding being formed by two continuous wires that joined together at their ends to thereby form one long filar that forms one of the parallel windings. The number of parallel windings is one less than the number of physical slots used to form each pole. Thus, for each wrap or turn the windings make about the stator core, the three windings can be used to fill each central slot, BB, CC and one of the outer slots, AA, BB as depicted in the illustrated embodiment. By forming all three windings with a phase shift end loop at a particular spot between two poles wherein the phase shift end loops are all one slot different than the standard pitch end loops, the wires can be shifted from the three most counterclockwise slots of each pole to the three most clockwise slots of each pole or visa versa.

For example, in FIG. 1, at the point where wires X, Y and Z transition from layer 3 to layer 4, all three end loops have a 10 pitch end loop that function as phase shift end loops. In other words, after completing two wraps or turns, the wires X, Y, Z have a phase shift end loop. This is also seen in FIG. 4 wherein at pole 15 in layer 3, wire X is in slot AA, wire Y is in slot BB and wire Z is in slot CC as a result of the 10 pitch phase shift end loops, wire X is in slot BB, wire Y is slot CC and wire Z is in slot DD at pole 16 in layer 4. In the illustrated example, these phase shift end loops occur at the point where the windings transition from layer 3 to layer 4. This is necessary to maintain the pattern wherein the windings are in slot AA in layers 1, 2 and 3 and are in slot DD in layers 4, 5 and 6. If an alternating pattern were employed for the two different phases in the outer slots, a larger number of phase shift end loops would be required.

Wires A, B and C also have phase shift end loops as can be seen with reference to FIGS. 2 and 4. After completing one wrap or turn, wires A, B, C have a phase shift end loop. This can be seen in FIG. 2 where the wires A, B, C transition from layer 3 to layer 4. This is also seen in FIG. 4 wherein at pole 16 in layer 3, wire B is in slot AA, wire C is in slot BB and wire A is in slot CC as a result of the 10 pitch phase shift end loops, wire B is in slot BB, wire C is slot CC and wire A is in slot DD at pole 1 in layer 4.

To provide an electrically balanced winding pattern, each of the parallel windings needs to be in each slot central slot, BB, CC, an equal number of times and needs to be in each outer slot, AA, DD, an equal number of times. For the illustrated embodiment, the fill ratio between the central slots, BB, CC and the outer slots AA, DD is 2:1 and, thus, each winding needs to be disposed in the central slots twice as many times as it is disposed in the outer slots. Position change end loops which shuffle the relative position of the windings in pole slots are used to achieve this balance.

In the illustrated example, each set of wires A, B, C and X, Y, Z are subject to position change end loops to alter the relative position of the wires at three locations for a total of six such locations. Turning first to FIGS. 1, 4 and 5, it can be seen that wires X, Y and Z are subject to three position changes. At the interval between poles 8 and 9 when wires X, Y and Z are in layer 1, a set of position change end loops are used to alter the relative positions of wires X, Y and Z. At this location, the end loop wire X has a pitch of 11 slots while the end loops for wires Y and Z each have a pitch of 8 slots. As a result, wire X moves from slot AA at pole 8 to slot CC at pole 9, wire Y moves from slot BB at pole 8 to slot AA at pole 9 and wire Z moves from slot CC at pole 8 to slot BB at pole 9.

Wires X, Y, Z are subject to another position change at the interval between pole 8 and 9 when the wires are in layer 3. See FIGS. 1 and 5. This position change involves wire X having a position change end loop with a pitch of 7 slots, wire Y having a position change end loop with a pitch of 10 slots and wire Z having a position change end loop with a pitch of 10 slots. As a result, in layer 3, wire X moves from slot CC at pole 8 to slot AA at pole 9, wire Y moves from slot AA at pole 8 to slot BB at pole 9 and wire Z moves from slot BB at pole 8 to slot CC at pole 9.

Wires X, Y, Z are subject to a third position change at the interval between poles 16 and 1 as the wires shift from layer 4 to layer 5. See FIGS. 1 and 4. This position change involves wire X having a position change end loop with a pitch of 11 slots, wire Y having a position change end loop with a pitch of 8 slots and wire Z having a position change end loop with a pitch of 8 slots. Each of these position change end loops also move wires X, Y, Z from layer 4 at pole 16 to layer 5 at pole 1. Thus, wire X moves from slot BB at pole 16 to slot DD at pole 1, wire Y moves from slot CC at pole 16 to slot BB at pole 1 and wire Z moves from slot DD at pole 16 to slot CC at pole 1. To provide an electrically balanced winding pattern, each of the parallel windings needs to be in each central slot BB an equal number of times, in each central slot CC an equal number of times, in each outer slot AA an equal number of times and in each outer slot DD an equal number of times. For a stator having more slots per pole per phase, the same pattern applies for the parallel wires to be electrically balanced.

Wires A, B, C are also subject to position change end loops. More specifically, and as can be seen in FIGS. 2 and 3, at the point where wires A, B, C shift from layer 2 to layer 3, the end loops extending between poles 15 and 16 are position change end loops. This position change involves wire A having a position change end loop with a pitch of 11 slots, wire B having a position change end loop with a pitch of 8 slots and wire C having a position change end loop with a pitch of 8 slots. Each of these position change end loops also move wires A, B, C from layer 2 at pole 15 to layer 3 at pole 16. Thus, wire A moves from slot AA at pole 15 to slot CC at pole 16, wire B moves from slot BB at pole 15 to slot AA at pole 16 and wire C moves from slot CC at pole 15 to slot BB at pole 16.

Wires A, B, C are subject to a second position change at the interval between poles 7 and 8 in layer 4. This position change involves wire A having a position change end loop with a pitch of 7 slots, wire B having a position change end loop with a pitch of 10 slots and wire C having a position change end loop with a pitch of 10 slots. Thus, wire A moves from slot DD at pole 7 to slot BB at pole 8, wire B moves from slot BB at pole 7 to slot CC at pole 8 and wire C moves from slot CC at pole 7 to slot DD at pole 8.

Wires A, B, C are subject to a third position change at the interval between poles 7 and 8 in layer 6. This position change involves wire A having a position change end loop with a pitch of 11 slots, wire B having a position change end loop with a pitch of 8 slots and wire C having a position change end loop with a pitch of 8 slots. Thus, wire A moves from slot BB at pole 7 to slot DD at pole 8, wire B moves from slot CC at pole 7 to slot BB at pole 8 and wire C moves from slot DD at pole 7 to slot CC at pole 8.

As mentioned above, the wiring diagrams in FIGS. 1 and 2 label any pitch between slot segments that is non-standard. The location of the number indicating the non-standard pitch also indicates at which axial end of the stator the end loop forming the non-standard pitch is located. FIGS. 1 and 2 also show from which axial end of the stator the beginning and end of wires A, B, C, X, Y, Z extend. As can be seen in FIG. 1, the position change end loops for wires X, Y, Z are all at the same axial end of the stator assembly as the start and finish lead ends of wires X, Y, Z with the phase shift end loops being positioned on the opposite axial end of the stator assembly. Similarly, as can be seen in FIG. 2, the position change end loops for wires A, B, C are all at the same axial end of the stator assembly as the start and finish lead ends of wires A, B, C with the phase shift end loops being positioned on the opposite axial end of the stator assembly. The start and finish lead ends and position change end loops of wires A, B, C, X, Y, Z are all on the same axial end of the stator assembly while the phase change end loops of wires A, B, C, X, Y, Z are all on the opposite side of the stator assembly.

It is additionally noted that when position change end loops are used with the wires, the individual wire having the largest pitch will be extended further axially than the wires with the shorter pitches and will have an end loop that extends over the shorter pitch and axially shorter end loops. In other words, if three wires have position change end loops with two wires having a pitch of 8 and one having a pitch of 11, the wire having a pitch of 11 will be extended axially further from the stator core than the two wires with the pitch of 8 and the end loop of the wire having a pitch of 11 will extend over the other two wires having a pitch of 8 to thereby avoid spatial conflicts between the wires.

While the described position change end loops are used to electrically balance the windings, it is noted that the wires A, B, C, X, Y, Z are not individually electrically balanced but once they are serially connected in pairs, the three resulting parallel windings are electrically balanced. In other words, each winding is formed by a series connection between two individual unbalanced wires to form a balanced winding. This is further discussed below with reference to Tables 3 and 4.

The wires are connected together at their finish ends. Thus, the end of wire A extending from layer 6 at pole 15 is connected in series with the end of wire Z extending from layer 6 at pole 16; the end of wire B extending from layer 6 at pole 15 is connected in series with the end of wire X extending from layer 6 at pole 16; and the end of wire C extending from layer 6 at pole 15 is connected in series with the end of wire Y extending from layer 6 at pole 16. The start leads of each of the wires are connected with an external circuit member. For example, start leads A, B and C may all be attached to a neutral connection with start leads X, Y and Z all being attached to a regulator, inverter or other circuit member. The start leads of the A, B and C wires all extend from layer 1 of pole 16 and are conductively coupled together, similarly, the start leads of the X, Y and Z wires all extend from layer 1 of pole 1 and are conductively coupled together. As a result the first winding (formed by the series connected pair of wires A and Z), the second winding (formed by the series connected pair of wires B and X), and the third winding (formed by the series connected pair of wires C and Y) are arranged in parallel. It is further noted that in the illustrated embodiment, each of the series connections, i.e., between A and Z, between B and X and between C and Y, is also a reversing connection with one of the wires extending in a clockwise direction about the stator from the series connection and the other wire extending in a counterclockwise direction about the stator from the series connection.

As can be understood with reference to the tables presented below, the winding pattern described above and shown in figures provides an electrically balanced stator assembly.

Table 1 presented below provides a detailed summary of the winding pattern for wires A, B, C of the winding pattern for wires X, Y, Z of a single phase of three phase electric machine 20.

TABLE 1 Winding Pattern for Wires A, B, C Slot Slot Slot Slot Slot Turn Layer Group AA BB CC DD Start 1 1 16 A B C Layer Change 1 2 1 A B C 1 2 2 A B C 1 2 3 A B C 1 2 4 A B C 1 2 5 A B C 1 2 6 A B C 1 2 7 A B C 1 2 8 A B C 1 2 9 A B C 1 2 10 A B C 1 2 11 A B C 1 2 12 A B C 1 2 13 A B C 1 2 14 A B C 1 2 15 A B C Layer and Position 2 3 16 B C A Change Slot Shift and 2 4 1 B C A Layer Change 2 4 2 B C A 2 4 3 B C A 2 4 4 B C A 2 4 5 B C A 2 4 6 B C A 2 4 7 B C A Position Change 2 4 8 A B C , 2 4 9 A B C 2 4 10 A B C 2 4 11 A B C 2 4 12 A B C 2 4 13 A B C 2 4 14 A B C 2 4 15 A B C Layer Change 3 5 16 A B C Layer Change 3 6 1 A B C 3 6 2 A B C 3 6 3 A B C 3 6 4 A B C 3 6 5 A B C 3 6 6 A B C 3 6 7 A B C Position Change 3 6 8 B C A 3 6 9 B C A 3 6 10 B C A 3 6 11 B C A 3 6 12 B C A 3 6 13 B C A 3 6 14 B C A Finish 3 6 15 B C A

Table 2 presented below provides a detailed summary of the winding pattern for wires X, Y, Z of a single phase of three phase electric machine 20.

TABLE 2 Winding Pattern for Wires X, Y, Z. Slot Slot Slot Slot Slot Turn Layer Group AA BB CC DD Start 1 1 1 X Y Z 1 1 2 X Y Z 1 1 3 X Y Z 1 1 4 X Y Z 1 1 5 X Y Z 1 1 6 X Y Z 1 1 7 X Y Z 1 1 8 X Y Z Position Change 1 1 9 Y Z X 1 1 10 Y Z X 1 1 11 Y Z X 1 1 12 Y Z X 1 1 13 Y Z X 1 1 14 Y Z X 1 1 15 Y Z X Layer Change 1 2 16 Y Z X Layer Change 2 3 1 Y Z X 2 3 2 Y Z X 2 3 3 Y Z X 2 3 4 Y Z X 2 3 5 Y Z X 2 3 6 Y Z X 2 3 7 Y Z X 2 3 8 Y Z X Position Change 2 3 9 X Y Z 2 3 10 X Y Z 2 3 11 X Y Z 2 3 12 X Y Z 2 3 13 X Y Z 2 3 14 X Y Z 2 3 15 X Y Z Slot Shift and 2 4 16 X Y Z Layer Change Layer Change and 3 5 1 Y Z X Position Change 3 5 2 Y Z X 3 5 3 Y Z X 3 5 4 Y Z X 3 5 5 Y Z X 3 5 6 Y Z X 3 5 7 Y Z X 3 5 8 Y Z X 3 5 9 Y Z X 3 5 10 Y Z X 3 5 11 Y Z X 3 5 12 Y Z X 3 5 13 Y Z X 3 5 14 Y Z X 3 5 15 Y Z X Layer Change and 3 6 16 Y Z X Finish

Table 3 provides a summary of the slot locations for each of wires A, B, C, X, Y, Z of a single phase of three phase electric machine 20 and illustrates how each of these individual wire are unbalanced.

TABLE 3 Slot Totals by Wire Slot AA Slot BB Slot CC Slot DD Total for A 16 16 1 15 Total for B 1 31 16 0 Total for C 0 1 31 16 Total for X 15 1 16 16 Total for Y 16 31 1 0 Total for Z 0 16 31 1

Table 4 provides a summary of the slot locations for each of the parallel windings which are formed by a series connection between a pair of the individual wires for a single phase of three phase electric machine 20. More specifically by joining wires A and Z into a single elongate filar, by joining wires B and X into a single elongate filar and by joining wires C and Y into a single elongate filar. Table 4 also demonstrates that the three resulting windings are electrically balanced.

TABLE 4 Slot Totals by Winding Slot AA Slot BB Slot CC Slot DD A and Z 16 + 0  16 + 16  1 + 31 15 + 1 B and X 1 + 15 31 + 1  16 + 16  0 + 16 C and Y 0 + 16  1 + 31 31 + 1  16 + 0 As can be seen from Table 4, the central to outer slot ratio for the windings is 2:1 but, as can be understood with reference to Table 3, the ratio between central slot and outer slot for the individual wires A, B, C, X, Y, Z are not 2:1. Table 4 shows how each individual unbalanced wire can be connected in series with another individual unbalanced wire to form a balanced winding.

FIGS. 7A through 9C illustrate end loops that can be used to achieve the winding pattern described above. It is first noted that FIGS. 7A-9C show the end loops of three wires as those end loops extend from a selected pole (pole A) to the next adjacent pole (pole B).

FIGS. 7A-7C illustrate the situation where three wires each define a standard pitch between the two poles. This is the most common arrangement of the end loops for the depicted electric machine. In this situation with all of the wires having a standard pitch, the wires maintain their same relative position in the two poles A, B. FIG. 7B, 7C illustrate this by showing fourth slot 50 of poles A and B. It is noted that while this empty slot 50 is shown on the left of the wires in FIGS. 7B, 7C, it will be on the right side of the wires at other locations.

When the wires undergo a phase shift and all of the wires have phase shift end loops, the pitch of each of the wires will differ from the standard pitch by one slot and the arrangement of the wires will look the same as depicted in FIGS. 7A-7C with each wire of the three wires defining the same pitch. For example, if the wires had an empty slot 50 at the left end at pole A and it was desired to shift the wires so that there was an empty slot 50 on the right end of pole B without changing the relative positions of the three wires, the wires would all be given a pitch of 8 (one less than the standard pitch). Alternatively, the wires could all be given a pitch of 10 (one more than the standard pitch) to move them from the three left slots of pole A to the three right slots of pole B without changing their relative positions.

FIGS. 8A-8C and FIGS. 9A-9C illustrate situations wherein each of the wires have a position change end loop. FIGS. 8A-8C illustrate the situation where one wire has a pitch less than the standard pitch and two wires have a pitch greater than the standard pitch while FIGS. 9A-9C illustrate the situation where one wire has a pitch greater than the standard pitch and the other two wires have a pitch less than the standard pitch. In each of these situations, the wires defining a greater pitch extend over the top of the wires having a less than standard pitch.

Turning specifically to FIGS. 8A-8C, the set of position change end loops depicted in these figures a first wire 52 moves from the right end of the wires at pole A to the left end of the wires at pole B. To accomplish this, first wire 52 has a pitch of 7, two less than the standard pitch while the remaining wires 54 each have a pitch of 10, one more than the standard pitch. This maintains the three wires, as a whole, in the same slots of poles A and B while rearranging the individual wires within those slots. In other words, the empty slot 50 of the pole is at the same side of pole A and pole B. FIGS. 8B and 8C illustrate the empty slot 50 being at the left end but the depicted arrangement of the wires in FIGS. 8A-8C will also maintain the empty slot at the right end of the poles.

While the depicted electric machine has three parallel windings per phase, alternative embodiments may include a lesser or larger number of parallel windings. To move one winding from the leading end of wires (at pole A) to the trailing end of the wires (at pole B) as depicted in FIGS. 8A-8C, the appropriate end winding, e.g., winding 52, is given a pitch that is equal to the standard pitch minus the number of remaining windings 54. In the case of FIGS. 8A-8C this will be 9−2 or 7 while the remaining wires are given a pitch that is equal to the standard pitch plus one or 9+1=10. Another way to state this formula is that winding 52 will have a pitch equal to the standard pitch, plus one and minus the total number of windings, or, (9+1)−3=7. The remaining windings are all shifted one slot to make room for winding 52 and, as mentioned above, have a pitch that is equal to the standard pitch plus 1. By giving the remaining windings 54 all the same pitch, these remaining wires 54 maintain their positions relative to each other.

As can be most easily seen in FIGS. 8B and 8C, the remaining wires 54 extend a greater axial distance away from the stator core and over wire 52. It also noted that similar to the wires of FIGS. 7A-7C, the remaining wires 54 have staggered apexes and a radially extending center section proximate the apex that allows them to overlap each other.

It is noted that, for the exemplary embodiment, the 7 and 10 pitch end loops depicted in FIGS. 8A-8C are employed with wires X, Y, Z in the middle of layer 3 (FIG. 1) and with wires A, B, C in the middle of layer 4 (FIG. 2). These sets of end loops are also present in FIG. 5, between poles 7 and 8, layer 4 for wires A, B, C and between poles 8 and 9, layer 3 for wires X, Y. Z.

Turning now to FIGS. 9A-9C, this set of end loops moves a first wire 56 from the left end of the wires at pole A to the right end of the wires at pole B. To accomplish this, first wire 56 has a pitch of 11, two more than the standard pitch while the remaining wires 58 each have a pitch of 8, one less than the standard pitch. This maintains the three wires, as a whole, in the same slots of poles A and B while rearranging the individual wires within those slots. In other words, the empty slot 50 of the pole is at the same side of pole A and pole B. FIGS. 9B and 9C illustrate the empty slot 50 being at the left end but the depicted arrangement of the wires in FIGS. 9A-9C will also maintain the empty slot at the right end of the poles.

To move one winding from the trailing end of wires (at pole A) to the leading end of the wires (at pole B) as depicted in FIGS. 9A-9C, the appropriate end winding, e.g., winding 56, is given a pitch that is equal to the standard pitch plus the number of remaining windings 58. In the case of FIGS. 9A-9C this will be 9+2 or 11 while the remaining wires are given a pitch that is equal to the standard pitch minus one or 9−1=8. Another way to state this formula is that winding 56 will have a pitch equal to the standard pitch, minus one and plus the total number of windings, or, (9−1)+3=11. The remaining windings 58 are all shifted one slot to make room for winding 56 and, as mentioned above, have a pitch that is equal to the standard pitch minus 1. By giving the remaining windings 58 all the same pitch, these remaining wires 58 maintain their positions relative to each other.

As can be most easily seen in FIGS. 9B and 9C, the first wire 56 extends a greater axial distance away from the stator core and over the two remaining wires 58. In both FIGS. 8A-8C and FIGS. 9A-9C it is the wires that have a larger pitch that extend over the top of the wires that have a shorter pitch. This arrangement is one that minimizes the spatial conflicts between the wires involved in the position change end loops. It also noted that similar to the wires of FIGS. 7A-7C and the remaining wires 54 of FIGS. 8A-8C, remaining wires 58 have staggered apexes and a radially extending center section proximate the apex that allows them to overlap each other.

It is noted that, for the exemplary embodiment, the 8 and 11 pitch end loops depicted in FIGS. 9A-9C are employed with wires X, Y, Z in the middle of layer 1 (FIG. 1) and with wires A, B, C in the middle of layer 6 (FIG. 2). An additional set of end loops that have 8 and 11 pitches but which also transition between layers are found at the transition between layers 4 and 5 for wires X, Y, Z (FIG. 1) and at the transition between layers 2 and 3 for wires A, B, C (FIG. 2).

It is noted that while the end loops depicted in FIGS. 9A-9C are used twice with each wire (four times with each winding) and the end loops depicted in FIGS. 8A-8C are used once with each wire (twice with each winding), other combinations of such end loops could also be employed to obtain electrically balanced windings.

Turning now to FIGS. 10A and 10B, these two figures illustrate an arrangement similar to that of FIGS. 9A-9C, but in FIGS. 10A, 10B, two of the wires 62 have a standard pitch of 9 and remain the same relative slot positions in both poles. The other wire 60 defines a pitch of 12 and moves from a position on the left end of pole A to a position on the right end of pole B. Thus, this arrangement not only alters the relative position of the three wires but also shifts all three wires within the poles from the three trailing slot positions (at pole A) to the three leading slot positions (at pole B) (a phase shift end loop). This is accomplished by having wires 62 retain the same slots in pole A and pole B by using a standard pitch with these two wires 62 and having wire 60 leapfrog over wires 62 by providing it with a pitch that is equal to the standard pitch, plus the number of wires over which it must leapfrog (2) plus one to move it into an empty slot, in other words, 9+2+1=12.

Similarly, the wires could be shifted from the leading slot positions to the trailing slot positions by providing the leading wire at pole A with a pitch of 6 (9−2−1=6) and the other two wires with a pitch of 9. In all of these situations, it will be most convenient to have the wires with the larger pitch extend over the top of the wires with the smaller pitch.

The depicted wires 62 have a configuration similar to the wires shown in FIGS. 7A-7C and have staggered apexes and a radially extending center section proximate the apex that allows them to overlap each other.

It is noted that the windings depicted in FIGS. 10A and 10B are not employed in the exemplary embodiment of FIGS. 1-6, however, the depicted electric machine could be modified to include windings similar to that shown in FIGS. 10A and 10B if desired. The use of the end loops shown in FIGS. 10A, 10B provide both a phase shifting and positioning changing function and thus the use of a single set of end loops as depicted in FIGS. 10A, 10B could be used to replace both a set of position change end loops and a set of phase shift end loops with a single set of end loops that combine both of these functions.

It is additionally noted, that while the depicted electric machine includes end loops that all have a cascaded arrangement, it would also be possible to employ interlaced/interleaved end loops (either continuous or hairpin) between poles which require only standard pitches for each of the wires and employ end loops as depicted in FIGS. 8A-8C, 9A-9C and/or 10A, 10B where appropriate.

While this invention has been described as having an exemplary design, the present invention may be further modified within the spirit and scope of this disclosure. This application is therefore intended to cover any variations, uses, or adaptations of the invention using its general principles. 

What is claimed is:
 1. A multi-phase electric machine comprising: a stator operably coupled with a rotor wherein the rotor is rotatable relative to the stator; the stator including a stator core defining a central opening and a plurality of axially extending slots which circumscribe the central opening; a plurality of windings mounted on the stator core wherein the plurality of windings define a plurality of phases and wherein, for each phase, the plurality of windings include: at least three parallel windings; the stator assembly defining a standard pitch between each pole of each phase, the pitch being a common circumferential spacing between corresponding slots of each pole; and wherein each of the parallel windings of each phase includes at least one position change end loop, wherein each of the parallel windings of each phase has one of the position change end loops at the same location, wherein the position change end loops define a non-standard pitch to thereby change the relative positions of the parallel windings in the slots.
 2. The electric machine of claim 1 wherein a first set of position change end loops is disposed between a selected pole and an adjacent pole and wherein a first winding of the first set of position change end loops is disposed at one of the clockwise and counterclockwise ends of the pole at the selected pole and is disposed at the other of the clockwise and counterclockwise ends of the pole at the adjacent pole, the remaining windings of the first set of position change end loops each being shifted one by one slot.
 3. The electric machine of claim 2 wherein the first winding defines a pitch that is greater than the standard pitch between the selected and adjacent poles and the remaining windings each define a pitch that is one less than the standard pitch between the selected and adjacent poles.
 4. The electric machine of claim 3 wherein the first winding extends over the remaining windings between the selected and adjacent poles.
 5. The electric machine of claim 4 wherein there are exactly three windings per phase and the first winding defines a pitch that is two slots greater than the standard pitch between the selected and adjacent poles.
 6. The electric machine of claim 2 wherein the first winding defines a pitch that is less than the standard pitch between the selected and adjacent poles and the remaining windings each define a pitch that is one greater than the standard pitch between the selected and adjacent poles.
 7. The electric machine of claim 6 wherein the remaining windings extend over the top of the first winding between the selected and adjacent poles.
 8. The electric machine of claim 7 wherein there are exactly three windings per phase and the first winding defines a pitch that is two slots less than the standard pitch between the selected and adjacent poles.
 9. The electric machine of claim 1 wherein, at each set of position change end loops, the windings defining a greater pitch extend over the windings defining a lesser pitch.
 10. The electric machine of claim 9 wherein the windings define a phase shift wherein for each pole, there are a greater number of slots than windings.
 11. The electric machine of claim 9 wherein each winding includes a plurality of position change end loops.
 12. The electric machine of claim 1 wherein the electric machine is a three phase electric machine. 